These tools can be setup so that they cannot be undone by (non-admin) users.

Control Log-in times

• timkpr

Web Content blocking

• Open DNS Family Shield
• Self Control
• get-shit-done
• Chomper
• Modifying /etc/hosts file for example here

List of domain names

These are classification of domain names in categories. They are useful if you would like to allow selected websites only based on content.

• Steven Black/hosts
• Blacklists UT

Web content filters

These too can block content based on blacklists, but can also filter content by examining it on the fly. These are http/https proxy servers. Access to internet should only be allowed via the proxy.

• Redwood
• e2guardian